The mission ofthe NICHD is to ensure that every person is born healthy and wanted, that women suffer no harmful effects from reproductive processes, and that ail children have the chance to achieve their full potential for healthy and productive lives, free from disease or disability, and to ensure the health, productivity, independence, and well-being of all people through optimal rehabilitation. Postpartum anxiety and depression-associated disorders can have negative effects on the health of both mother and offspring through effects on matemal behavior, and little is known about the etiology of these disorders. Although chronic stress is a significant risk factor for depression, it is unknown how chronic stress during lactation affects maternal behavior. Recent molecular studies indicate that the neurohormones arginine vasopressin (AVP), oxytocin (OXT), and corticosteroid releasing hormone (CRH) may be involved in the modulation of maternal behavior in lactating rats. It is hypothesized that the central AVP system may be a potential target for the treatment of postpartum behavioral disorders, as central manipulations of AVP alter behavior. The overall objective of the current protocol is to investigate the role of AVP in postpartum maternal behavior and aggression, and the effects of social stress on this system. The specific aims ofthe current proposal are to characterize the roles of central AVP, OXT, and CRH in the control of maternal behavior and maternal aggression, investigate the effects of chronic social stressors on these behaviors and central AVP, and investigate a potential AVP-mediated mechanism forthe effects of chronic social stress on maternal behavior. These aims will be pursued using behavioral, endocrine, physiological and molecular methods to quantify the effects of chronic social stressors, molecular and imaging (fMRI) techniques to identify the neural regions implicated in the acute and chronic control of maternal behavior, and stereotaxic surgical techniques to manipulate central AVP activity. The overal goal is to gain valuable training in behavioral) neuroscience techniques and study the neuropeptidergic control of behavior. The long term career goal is to develop new targets and treatments for behavioral disorders of mothers.